1. Field of the Invention
The present invention generally relates to a technology for transferring a servo pattern recorded on a master medium onto a magnetic recording medium.
2. Description of the Related Art
A recording density of a magnetic disk device is getting higher for a high capacity year by year, which makes it difficult to produce servo data serving as head positioning data with high precision. However, to reduce a manufacturing cost for a magnetic disk, it is required to easily produce the servo data with high precision.
One approach is to use a master medium and a slave medium. The master medium has servo patterns indicative of servo data formed on its surface. The slave medium is a magnetic recording medium. The slave medium is closely placed on the master medium and a magnetic field is applied to both of them. As a result, the servo patterns can be magnetically transferred from the master medium to the slave medium.
A conventional technique of producing such a master medium is disclosed in Japanese Unexamined Patent Application Publication No. 2001-256644.
According to the conventional technique, when ON/OFF of the servo data are formed with two types of magnetic patterns of opposite magnetic directions, if magnetic patterns having the same direction include contact points for each other, the transferred servo patterns become unstable and easily collapsed.
Besides, when the magnetic patterns having the same direction are arranged in succession, the servo patterns become unstable and easily collapsed, causing a noise around an area where the magnetic patterns are arranged in succession.
In addition, when the servo data is formed with an oblique line pattern in which oblique lines sandwiching a boundary line with a constant angle to the boundary line, because the angle is constant with respect to the boundary line, the oblique line pattern is formed along a circumference of a track as it goes to a circumference of the magnetic disk. As a result, a magnetic component in a cosine direction of an applied magnetic field for transferring the servo data (i.e., a tangential component of a track) is decreased, decreasing an intensity of magnetization. Furthermore, when reading the servo data, it is difficult to read the servo data because magnetic flux components are small in a cosine direction of reading the magnetic information.